The present invention is related to a tread for a vehicle tire. In particular, the present invention relates to improvements to the tread of an automobile or light truck tire which is particularly well adapted for winter travel under snowy and icy conditions.
Winter or snow tires have historically been designed with treads having large traction lugs that were widely spaced yielding a very low road contacting surface within the tires normally loaded footprint. These open tread patterns are excellent in deep snow. However, due to the large lugs and open tread pattern these tires are notorious for generating substantial noise and vibration when used on rain soaked or dry paved roads. The tread wear rate is rapid and therefore these tires are considered for use only during the snowy winter months. These tires are not particularly well suited for icy road conditions.
Many driving enthusiasts have chosen to use all season type treads. These tread patterns employ wide transverse grooves and circumferential grooves defining discrete tread elements. The tread patterns are substantially more closed than a pure snow tire yet are sufficiently open to provide good snow traction and overall acceptable tread wear and noise performance. The primary advantage to the all season tread is that the tires can be used year round. A fundamental disadvantage is that the tires are not as good as snow tires in severe winter conditions and can be particularly poor in icy or freezing rain conditions.
Under these icy road conditions metal studs or cleats are considered the optimal traction solution. Unfortunately in many localities the use of such traction aides is prohibited because of the tremendous road damage that can result and in those areas where these types of studded tires are permitted the legal use is generally limited in duration.
The use of treads having a high density of sipes within the traction elements has been determined to provide a good improvement to both snow and ice traction performance. Such heavily bladed tires can exhibit good winter ice traction performance by providing an increase number of tread edges to provide forward traction.
One particularly significant prior art winter tire exhibiting the employment of multiple bladed sipes combined with a plurality of circumferential and transverse grooves is disclosed in U.S. Pat. No. 5,198,047. This tire, commonly known as the Goodyear Ultra Grip 4 Tire, has a directional tread pattern. That is the tread had a preferred direction of travel adapted to yield superior traction in one direction. This directional tread pattern was symmetrical about the equatorial plane of the tire. The sipes were arranged angularly similar within each tread half and oppositely tread half to tread half to further enhance the directional traction performance by insuring a first portion of the sipe always enters and leaves the footprint prior to the second or trailing portion. The tire has demonstrated excellent directional traction and reasonable noise properties. The tire tread of the present invention although useable in these directional type tread patters is especially well adapted to provide excellent all direction travel thus making the tread nondirectional, which is a most beneficial feature in a winter tire.
The present invention employs narrow transverse grooves and a novel arrangement of wavy sipes so as to achieve a winter tire having excellent snow and ice traction properties in all directions of travel including forward, backward and during turning or cornering maneuvers. The tread pattern also exhibits very low noise and has interlocking traction elements that greatly reduces the Residual Self-Aligning Torque (RSAT) that is commonly exhibited in such tires.